More Life Years Lost Through Smoking Than HIV in 18,000-Person Analysis

CROI 2014, March 3-6, 2014, Boston

Mark Mascolini

Antiretroviral-treated HIV-positive people lost more life years compared with the general population because of smoking than because of HIV infection, according to analysis of nearly 18,000 HIV-positive people in the ART Cohort Collaboration (ART-CC) [1]. The impact of smoking on mortality rose steeply with age.

ART-CC investigators noted that cardiovascular disease and non-AIDS cancers have become major causes of death in HIV populations since combination antiretroviral therapy (ART) arrived. Thus they proposed that "the impact of smoking on life expectancy may have become substantial." That proposal seems all the more likely given the high smoking rates in many HIV populations.

To assess the impact of smoking on mortality with HIV infection, the ART-CC team analyzed deaths in eight HIV cohorts in Europe and North America, excluding people who became infected while injecting drugs. They defined baseline as the later of two dates: 1 year after starting ART or the date when smoking status was ascertained. People classified as smokers at baseline remained smokers throughout the analysis. The ART-CC team estimated life-years lost to HIV by comparing life expectancies in HIV-positive people and the general French population.

The analysis included 10,767 HIV-positive smokers (60% of the HIV group) and 7228 HIV-positive nonsmokers. Median follow-up reached 4.3 years in smokers and 3.7 years in nonsmokers. Men made up 81% of smokers and 57% of nonsmokers. Median age at baseline was 40 in smokers and 38 in nonsmokers. A higher proportion of smokers than nonsmokers (45% versus 30%) became infected with HIV during sex between men. Similar proportions of smokers and nonsmokers (72% and 69%) had a viral load below 400 copies.

During follow-up 520 people died of any cause to yield a twice higher mortality rate ratio (MRR) in smokers than never-smokers (MRR 1.94, 95% confidence interval 1.56 to 2.41). Among cohorts with data on current and previous smokers, current smoking raised the death risk 70% compared with never-smokers (MRR 1.70, 95% CI 1.23 to 2.34), whereas previous smokers and never-smokers had a similar death rate.

The AIDS-related death rate was not significantly higher in smokers than never-smokers, but smokers had significantly higher rates of death from non-AIDS malignancies (MRR 3.13, 95% CI 1.80 to 5.45), cardiovascular disease (MRR 6.28, 95% CI 2.19 to 18.0), and liver disease (MRR 8.70, 95% CI 1.14 to 66.6).

The researchers calculated that a 35-year-old man with HIV lost 5.9 years of life because of HIV (95% CI 4.9 to 6.9) compared with the general French population. In contrast, an HIV-positive 35-year-old man lost 7.9 years of life because of smoking (95% CI 7.1 to 8.7). A 35-year-old HIV-positive nonsmoker with a viral load below 400 copies could expect to live another 43.5 years (95% CI 41.7 to 45.3), whereas a 35-year-old HIV-positive smoker with a sub-400 viral load could expect to live only another 35.0 years (95% CI 34.2 to 35.8).

Compared with the general French population, excess mortality per 1000 person-years resulting from smoking jumped from 0.6 (95% CI -1.3 to 2.6) at age 35 to 43.6 (95% CI 37.9 to 49.3) at age 65 or older.

The ART-CC team cautioned that their analysis is limited because of the need to exclude cohort members without smoking data. They also noted that smoking may not directly account for the shortened life expectancy of these HIV-positive people but may be a marker of related lifestyle risk factors.

With those caveats in mind, the researchers concluded that "treated HIV-infected individuals may lose more life years through smoking and associated lifestyle factors than through HIV." Because smoking-related excess mortality rises sharply with age, they warned that "increases in smoking-related mortality can be expected as the treated HIV-infected population ages."